1. Field of the Invention
This invention relates to the field of electrically programmable and thermally reprogrammable read-only memories.
2. Prior Art
The electrically programmable and reprogrammable read-only memories of the semiconductor-type comprising semiconductor integrated circuits in which the programmable memory element is a floating gate storage transistor are illustrated, for example, in U.S. Pat. Nos. 3,744,036 and 3,938,108. Non-reprogrammable semiconductor memories are known to include devices having a fusible link usually in a transistor emitter lead. A fusible link is fabricated by using a special material such as polycrystalline silicon, nichrome or titanium-tungsten. Programming the memory cell associated with a given fusible link is accomplished by passing an excessive amount of current through the fusible link causing it to open. In another form of nonreprogrammable read-only memory, an excess current is applied to the base collector emitter region forcing an internal breakdown in a base emitter junction. A breakdown melts nearby chip metallization and aluminum flows into the junction causing a short-circuit.
The present invention describes a memory cell and a memory array comprised thereof having as a programmable element a mixture of finely divided metallic material dispersed in a thermoplastic resin. The programmable element is initially substantially nonconductive and may be rendered or programmed conductive by forcing an electrical current therethrough for a sufficient period of time. The programmable element may be returned to its substantially nonconductive state by heating to a temperature relatively high with respect to the normal temperature use of the programmed memory cell.